In view of the REINDEX-on-pg_class kerfuffle that we're currently sorting through, I was very glad to see that the concurrent reindex code doesn't even try:
regression=# reindex index concurrently pg_class_oid_index; psql: ERROR: concurrent reindex is not supported for catalog relations regression=# reindex table concurrently pg_class; psql: ERROR: concurrent index creation on system catalog tables is not supported It'd be nice though if those error messages gave the impression of having been written on the same planet. (It might be worth comparing wording of other errors-in-common between what are evidently two completely different code paths...) regards, tom lane